4分之1加28分之1加70分之1加130分之1加208分之1怎么简便计算?

1/4+1/28+1/70+1/130+1/208=1/(1*4)+1/(4*7)+1/(7*10)+1/(10*13)+1/(13*16)=1/3*[(1/1-1/4)+(1/4-1/7)+(1/7-1/10)+(1/10-1/13)+(1/13-1/16)]=1/3*(1-1/16)=(1/3)*(15/16)=5/16